SP3-3 Influence of Orifice Diameter on Spray and Combustion using a Fast Diesel Common Rail Injector(SP: Spray and Spray Combustion,General Session Papers)

Abstract

This was accomplished with a prototype injector that achieves a faster injection rate of approximately 80% or more than a mass-production model piezo-driven common rail injector that complies with EURO 5 standards by enhancing the injection rate from the opening of the nozzle needle up to full lift while keeping the nozzle hole diameter small. The prototype injector achieved this by making the fuel-air mixture leaner without increasing the fuel injection pressure, or in other words without an adverse effect on fuel consumption due to increased work by the fuel pump, and thus yielded a reduction in harmful emissions. This was confirmed by evaluation of the spray characteristics and by combustion experiments using a single-cylinder engine, the results of which were reported. In this paper, the influence of orifice diameter using a micro orifice nozzle is described by spray measurement and engine combustion. With the use of practical multi-hole nozzles, whose orifice diameter are 0.08mm, 0.10mm and 0.12mm respectively, spray form observation, fuel droplet size measurement and combustion experiment using single-cylinder engine were conducted. Downsizing of nozzle orifice diameter provides short liquid phase penetration, narrow spray angle and small size fuel droplets. But soot from engine with 0.08mm nozzle is higher than those of 0.10mm and 0.12mm nozzles. This is considered that the influence on the combustion due to the reduced spray penetration is greater than atomization by the decreased diameter of the nozzle hole